The conventional art has focused on the use of chiral nematic liquid crystal that exhibits a cholesteric phase as a display medium. Because this type of liquid crystal has a memory capability, power is needed only when image is drawn, and the supply of power may be terminated when the display of an image is being maintained, making it ideal for low energy consumption. It is also capable of color and large-screen display. Therefore, it may be widely used in small to large items, i.e., from portable terminal devices such as electronic books to indoor or outdoor billboards or bulletin boards.
However, because this type of liquid crystal has a memory capability, where it is equipped with a power supply unit that entails an unstable supply of power, such as a dry battery, a battery or a solar battery, if the power supply runs out while an image is being redrawn, or if the supply of power is terminated due to insufficient charging, the image becomes stored in the memory in an incomplete or distorted fashion. While this might not be a significant problem where the user is an individual, it would appear very unsightly on a display used in a public location.
Moreover, where the screen can be reset to a prescribed display condition or a different display can be made to appear once the reset operation is performed, the following problems may occur: the screen present when the reset operation was performed may remain on the screen without display information, or some of the previous display may remain on the supposedly reset screen.